DJGhost the use of the compass would only be able to detect a magnetic field.What you would be looking for is the compass to spin around rapidly.At that point I would take some pictures and try for a good EVP. I myself have a CellSensor and I use it to eliminate things such as faulty light switches,tv,microwaves, etc. The only other advice I can give is don't rush out to buy equipment that you don't need just yet.

If you're low on funds and relatively new to the field...a compass would work just fine for now. When exposed to a magnetic field, it'll start spinning or shaking.

However, I would go ahead and invest in an actual emf meter if you're serious about pursuing investigation. A meter will give you a numerical readout, which will paint you a much more detailed picture of what you're dealing with.

Keep in mind, however, that the idea that ghosts "cause" emf spikes is still debateable. Your best use of an EMF meter in this stage is to find sources of high em. High dosage and even lower dosage over a period of time can cause hallucinations, feelings of dread and paranoia, nausea, dizziness, etc.

However, if you DO get an unexplainable spike...dilligently try to rule out all other sources, including living persons, record it, and take temperature readings, audio, video, and snapshots to try to draw some correlation with the spike.